Well, Cotton likes to retain moisture, like you said. The old saying for hikers/hunters is "cotton Kills". Atleast that's what I know. If it's going to be, say, +45 degrees for most of the time, definatly go to cotton, because it will be warm enough you won't get cold. If it's < 35, definatly go with the poly/underarmour/synthetic stuff. It doesn't stink that bad and it will keep you warmer 'cause it lets go of the moisture and doesn't let it cool against your body. In between it's your call. Best of luck,
BigBuck95